Since the "land between the rivers" was not really that ideal, what would be considered the most significant environmental/geographical factor that contributed to the development or the diffusion of Mesopotamia?
I have read most of the information in e-notes about Mesopotamia, and I still am not sure of the answer to this question. Any references would be most appreciated also! Thank you
Fertile soil, easy and ready access to irrigation (along with its subsequent development) and the ability of such agriculture to sustain large herds of animals led to the growth and prosperity of Mesoptomaian society. Think for a moment, if that society would have been nearly as successful on the Arabian Peninsula. This points us back to the importance of those two rivers, the Tigris and Euphrates, to the viability of the civilization.
Northern Mesopotamia is made up of hills and plains. The land is quite fertile due to seasonal rains, and the rivers and streams flowing from the mountains. Early settlers farmed the land and used timber, metals and stone from the mountains nearby.
Agriculture. After 8000 BCE Near Eastern environments become substantially more attractive for human settlements. The Atlanticum is the period in which agriculture developed in the Near East, around the Nile in Egypt and in the Indus valley in India. The use of agriculture is expanding gradually further to the north and west. The Atlanticum is followed by a climate of lower temperature and precipitation. One of the relative cold and dry periods (4000-3000 BCE) coincides with the expansion of cities in Mesopotamia and the foundation of the first Egyption dynasty.
Climate determinism. Many attempts have been made (particularly in the early parts of this century) to explain the course of history as a result of large scale climatic change. These theories are called climate determinism. The modern equivalent of this is an explanation from an ecological perspective, in which still external influences (change in natural environment, now including e.g. deforestation etc) are the driving factor. Another school emphasizes the interhuman relations and sociological changes as the dominant process. It is now clear that a combination of these and additional factors play a significant role (cultural changes, technological innovations, new tools). However, a new hot and dry period, starting around 500 BCE, which hastens environmental changes (overgrazing and deforestation) probably did contribute to weaken the Mesopotamian civilization and caused the ''center of civilization'' to move to northern latitudes.
In Guns, Germs, and Steel, Jared Diamond argues that the development of Mesopotamia was due largely to the existence of many domesticable plants and animals. He says that there were many grasses with large seeds, for example, that could be domesticated as well as many relatively large animals that could be domesticated as well. This allowed farming to develop first (as far as we know) in that area. The development of farming led to a larger population density which, in turn, led to the onset of "civilization."
If you are inclined to accept that sort of argument, I would look at relevant parts of Diamond's book.